(1) Field of the Invention
The present invention relates to manufacturing of a semiconductor chip, and especially to a semiconductor device that prevents a defect at the time of manufacturing by filling in resin into a via hole of a semiconductor chip and its manufacturing method.
(2) Description of the Related Art
Up to now, a compound semiconductor device made of Field Effect Transistors (hereinafter, referred to as FET) or hetero bipolar transistors (hereinafter, referred to as HBT) has long been used as a high output power amplifier for transmission in a part of a cell phone, in which outstanding characteristics such as high output, high gain and low distortion are required. To meet this requirement, and especially to earn higher gain, together with upgrading a semiconductor element such as an FET, in a manufacturing process, a ground wiring is not pulled out from an electrode pad on a chip by a wire, but through a via hole that penetrates the chip from the reverse side. When a source electrode of an FET for amplification is grounded using this technique, it is possible to significantly reduce parasitic source inductance and increase a gain of a power amplifier.
Hereinafter, a manufacturing method of a semiconductor device having a via hole structure is explained using a cross-sectional view shown in FIG. 1.
For a start, as shown in FIG. 1A, on a surface of a GaAs substrate 100 on which a circuit made up of an FET, resistance, a capacitor and an inductor is formed, a hole 110 to be a via hole is formed with a depth of about 150 μm. Then, after Au plating 120 is formed on a part of an electrode and the hole 110 to be the via hole, a protective film 130 is formed on the top surface. At this time, it is more advantageous to form the hole 110 to be the via hole on the surface of the GaAs substrate than on the reverse side of the GaAs substrate in terms of simplicity of process.
Next, as shown in FIG. 1B, the hole 110 to be the via hole is penetrated by grinding the GaAs substrate 100 so that the substrate becomes an approximate 100 μm-thin film and so that a via hole 140 is formed. Then, laminated metals, Cr and Au, are evaporated on the reverse side of the GaAs substrate 100 and a reverse electrode 150 is formed. Then, although it is not illustrated, the GaAs substrate 100 is dice-cut into chips.
Next, as shown in FIG. 1C, a chip is dice-bonded on an assembly substrate 160 via an adhesive metal 170, either Ag paste or AuSn paste.
In the process of dice-bonding the chip included in the manufacturing method of the semiconductor device, the adhesive metal 170 spurts out from the via hole 140 and pollutes a circuit on the surface of the chip.
As a prior art arrangement to solve this problem, “Manufacturing Method of Semiconductor device” (refer to Japanese Laid-Open Patent application No. 2001-110897) was developed. According to that reference, in the manufacturing method shown in FIG. 1A, the hole 110 to be the via hole is filled in with photocuring resin. In the process shown in FIG. 1B, a reverse side electrode is formed all over the reverse side of the GaAs substrate 100 including a via hole aperture, which is covered with the reverse side electrode, and then the photocuring resin is removed with organic solvent. Thus, spurting out of the adhesive metal 170 at the time of dice-bonding is prevented.
In the conventional manufacturing method of a semiconductor device, however, the GaAs substrate is soaked in organic solvent and dried when the photocuring resin is removed, so there is a problem in that it is difficult to handle the GaAs substrate because it becomes a thin film and breaks. Additionally, in the conventional manufacturing method of the semiconductor device, the spurting out of the adhesive metal is prevented by the reverse side electrode. However, there is a problem in that when the reverse side electrode is thin, it is not sufficient to cover the via hole aperture; holes open up in the reverse side electrode; and the adhesive metal spurts out. On the other hand, when the reverse side electrode is thick, it is difficult to dice-cut. Furthermore, in the conventional method of manufacturing the semiconductor device, the photocuring resin fills in only the via hole, and the via hole aperture on the surface of the GaAs substrate is not fully covered with the photocuring resin. In that case, there is a problem in that when the adhesion between the plating on the sidewall of the via hole and the photocuring resin is weak, the spurting out of the reverse side metal to the surface of the chip occurs at the time of the vapor deposition of the reverse side electrode.